Stereoscopic and stroboscopic gunnery fire control system



Jan. 8, 1952 T. D. TYRA 2,581,459

STEREOSCOPIC AND STROBOSCOPIC GUNNERY FIRE CONTROL SYSTEM Filed Sept. 1, 1942 2 SHEETS-SHEET l FIG].

INVENTOR THOAS D. TY

BY 77% my? ATTO NEY T. D. TYRA 2,581,459

STEREOSCOPIC AND STROBOSCOPIC GUNNERY FIRE CONTROL SYSTEM Jan. 8, 1952 2 SHEETS-SHEET 2 Filed Sept. 1, 1942 1 INVENTOR 9b 4 27b THA 7ZATTORAEY b BY Patented Jan. 8, 1952 S-ZTEREQSCOPIC AND 'STRQBQSCQPIC GUN NER'Y FIR-E 'QONTROLSYSTEM Thomas D. Tyra, UnitedStatesNavy Applicationseptember 1, 194.2,Setial Nor45E8G3 (clfifisfil') (Granted under the act or March 3, I883, as amended April 3 1928; 37 0 Q. G. 757) 2 -Claims.

This invention relates to ordnance and more particularly to a new and improved system ot g-unnery fire control which is capable of extending the normal limits of depth perception of the human-eye, to rendernmre precise and accurate the prior art systems of fire control that make visible a. -portion or the trajectory and rely upon the gunners skill in directing the visible portion of the'tra-jectoryinto intersection of the moving target.

The iundamental problem in all gunneryis to so train and elevate the guns that the trajectories of thebullets will pass through the targets. In all for-ms of fire control the ability of the hu man eye to see is used. In conjunction there-.

with, and dependingupon the complexity of the installation, there may be ring sights, post sights. cross hairs, range finders, range and deflection predictors, etc. The function of all these devices is to use the information which is obtained by visual perception and then introducing estimated or known corrections for the many variables inyolved, to furnish information whereby the gun may be trained and elevated. When firing against aircraft targets, it is essential that all this be done with accuracy and rapidity.

In most forms of sights the only use made of the property of vision is the ability of the operator to determine when two or more objects are in line. This is normally accomplished by one eye acting alone. However, when both eyes are used together and within certain limitations, the value of the eyes is extended to include an additional phenomenon known as depth perception. The underlying principle upon which the functioning of this invention is based is this ability of the eyes to perceive depth, a property which is only possible with two-eyed vision. In conjunction therewith, in the preferred form of the invention, it is proposed to use tracer am.- munition to render visible a portion of the trajectory of at least some of a series of projectiles fired from a' gun; and to lei-optically view the target and this visible portion of the trajectory through a stereoscopic gun sight. By means of this gun sight the target and visible portion of the trajectory are viewed along converging lines of sight that have a spacing at the gun which greatly exceeds the interpupillary distance of the observer's eyes so that the fire control problem depicted to the observer is given the efiect of solidity or depth. Moreover, the system of fire control of this invention utilizes stroboscopiceifectsas well as stereoscopic effects to make the projectiles appear stationary in space so that the gunner in "such a .manner that he will instantaneously and without-conscious efiort, point his gun so as to obtain hits.

As noted above reliance placed upon the ,phe nomenon bYyXVhih depth-perception is increased; i. e. by en-tending the d-istance between the two points from which observations are to be made. Depth perception ,is :also increased bymagnification. Therefore; by means of anoptical systern of prisms and magnifying lenses, somewhat resembling the usual --range .finder, a great increase in depth perception isobtained.

Another {factor in the sighting of a gun is the acoommodationof the eyes to a rapidly moving object. Becauseofthe lack of sufiicient accommodation, together with persistence of vision, a tracerbullet cannot be :followed by the eye, but its ;=entire trajectory is retained in the eye as a single image.

Ehe invention also assists in overcoming the lack of accommodation of the eyes by intermittently cutting ofi the image observed by the eyes.

;It.-istherefore an-objectgof this invention to ex tend the normallimits-of-depth perception of the human-eyes.

ltisalso an objector this-invention to increase the :range atwhi'ch hits may-be obtained by a gunner.

A furtherobject of thei-nventionis to increase hezimmbernf hitszobtained :by a. unner firing a.m defi iinggunatzany range.

Still :further objects, advantages, and improvements will'be apparent from the following description .of the invention taken in connection with the accompanying drawings, of which:

Figure -1-is a perspectivephantom View of the sight mounted-one machine gun of conventional design.

Figure'2is a side view of the rear portion of a conventional --machine gun showing a side view of the sight as well as a'suggested placement of its operating switch.

Figure 3 is a vertical cross sectional view of the sight taken along the line '3-3 of Figure 5.

Figure' gishows the interior arrangement of the operatin witch shown m figu Flgurefi is a horizont'alcrossesectional view of the sight enalqn' the line 5.4 of Figure 3.

gun for convenience, although it is to be understood that the sight may be used with any type of gun and may be mounted in any convenient position not necessarily in association with the gun.

The main body of the sight comprises a longitudinal binocular casing l3 and a shutter casing l4 suitably joined together. As shown in Figs. 2

and 3 the sight is shown mounted-on the backplate of the machine gun by means of the metal strip !5. This strip is attached to the backplate by means of a stud l'i and-a spacer l8 made of suitable resilient material. While the present embodiment of the invention shows the sight attached to the backplate of a machine gun, it will be understood that it could be mounted on any other convenient portion of a gun or in a position independently of the gun, the only criterion being that the space near the eyepieces of the sight be clear so as to permit an observer to place his eyes in the proper position to use the sight, as shown in Fig. 2.

The optical system of the sight can be seen more in detail in Figs. 3 and 5. It consists essentially of a binocular comprising the objective lenses Ito and I91) mounted in suitable openings provided in the forward portion of the binocular casing [3. These lenses are spaced apart a distance greater than the normal interpupillary distance. Total reflecting prisms Zla, 22a, 2| b, and 22?), mounted within the binocular casing l3 in the position shown, transmit the images received from lenses Na and I91) to the field lenses 23a and 23b, respectively, of the eyepiece system, which lenses are mounted in suitable openings provided in the binocular casing 13. The images then pass through a shutter system, later described, to the eyepiece lenses 24a and 24?) which are mounted in suitable openings in the shutter casing i 4. Flexible eyepieces 25a and 25b of rubber or other suitable material may be provided to shield the eyepiece lenses 24a and 24b. The optical system described illustrates the fundamental principle involved and it will be understood that suitable arrangements for focusing the lenses, and other refinements may be provided.

The shutter system is contained within the shutter casing 14 as shown in Figs. 3, 5, and 6. The object of the shutter is to provide for simultaneous interruption and reconstructionof the images as they pass through the eyepiece systems. Any suitable mechanism which will accomplish this result will be effective but for illustration a preferred type will be described.

Simple shutter plates 26a and 26b constructed of some magnetizable material such as steel, are swingably supported within the shutter casing M on pivots 21a and 21b. These pivots 21a and 21b are each mounted on one fof the extremitie's'of a pair of C-shaped 's'olenoid's28a and 28b made of suitable magnetic material 'and suitably supported within the shutter casing 14. Suitable coils for energizing the solenoids are shown at 29a and 29b. The shutters 21a and 211) are constructed so that their free ends will extend across the gap in the solenoids and thus be attracted toward the unobstructed ends of the solenoids whenever a current is passed through the coils 29a and 29b.

The solenoids 28a and 28b are so placed within the casing 14 that when the shutter plates 26a and 26b are aligned across the gap in the solenoids they effectively cut off the passage of light to the eyepiece lenses 24a and 24b. Coil springs 3 la and 312) are pivotally attached to the solenoids by pivots 32a and 32b and to the shutter plates by pivots 33a and 33b. These springs exert a pressure which tends normally to move the shutter plates 26a and 26b to a position on either side of the line of sight to the eyepieces. Stops 34 are provided to limit the amount of this movement. Thus, if the shutter plates are in the position as shown by the full lines in Fig. 6 and an electric alternating or direct current is caused to flow in the coils 29a and 291), the shutter plates tend to be drawn away from the stops 34 and to align themselves with the ends of the gaps in the solenoids, as a result of magnetic attraction, thus obstructing the view through lenses 23a and 23b.

As long as the coils 29a and 29b are electrical- 1y energized, the magnetic attraction of the solenoids 28a and 28b will tend to maintain shutter plates 26a and 26b in a position to cut off the light image. However, as the shutter plates 26a and 26?) move away from stops 34 toward their positions of alignment across the gaps of the solenoids 28a and 28b the alternating current is decreasing in magnitude or the direct current is at this point interrupted so that inertia will carry the shutters past the point of alignment. The springs 3la and 3lb will now move the shutters into the positions against the stops 34 on the other side of the position of alignment as shown by the dotted lines. On the succeeding cycle the alternating current will be increasing in value (positive or negative) or the direct current will commence to flow again re-energizing the coils so that the cycle of operation will be repeated. If the duration of current flow is maintained for more than a very short period and the shutters are caused to remain fixed in alignment with the ends of the solenoids, the springs 31a and 3| b will not necessarily force the shutters back against the stops 3 on the side of the point of alignment opposite to that from which they first moved, it being immaterial on which side the shutters come to rest.

An examination of the diagram in Fig. 7 will show an electrical circuit which is suitable for the purpose, though not to be construed as the only one which could be used. A source of electric energy, such as a battery or generator is shown at G, and a switch is represented at S. The coils 29a and 2% are connected in series with each other and with the switch S and source of electricity G by means of the conductors 35, 3B, 31, and 38. A condenser C is shown connected across the switch S in order to minimize arcing, but this is not essential to the operation of the device.

It has been found suitable for operation of the sight to have the shutters operate at each firing of the associated gun. However, the sight. does not depend for its results upon the synchronization of firing of the gun with the operation of a shutter operating at substantially constant speed.

The present sight would be operable even if the operation of the shutter plates was entirely independent of the operation of the gun. However for the purpose of illustrating the invention, one means of operation will be described, whereby the switch S (Fig. 7) is caused to close, thusactuating the shutters 26a and 26b each time the gun fires.

Switch S comprises a casing 39 (Fig. 4) within which are mounted insulating blocks 4| and 42. A fixed electrical contact 43 is mounted on the insulating block 4| while a movable electrical contact 44 is mounted on the block 42. A stud 45 is attached to one end of contact 44 and projects through a suitable opening provided in the side of the casing 39. This switch S is mounted on the side of the receiver of a machine gun (as shown in Fig. 2) so that when the bolt B reaches the rearward end of its travel (as shown by dotted lines in Fig. 4) it will engage the stud 45 and move the movable contact 44 into connection with the fixed contact 43. Inasmuch as the bolt B is caused by the internal mechanism of the gun to make a complete cycle of movement backward and forward during the period between the firing of each cartridge the shutters 26a and 26b of the binocular sight will be caused to operate once for each firing of the gun.

In the operation of the sight its preferable that a certain proportion of tracer bullets should be included in the ammunition for the gun. The

gunner will observe the flight of these tracers through the binocular sight as shown in Fig. 2. Assuming that the shutter mechanism is being operated by the action of the bolt B as already described, or by some other suitable arrangement, the observed flight of the tracers will appear not as a curved line but as a series of dashes appearing as portions of the normal trajectory. This effect is shown in Fig. 1 by the interrupted curves 46a, 46b, 46c, 46d, and 46a, while the dotted lines represent the sight lines from the dashes 46a, 46b, and target T.

Under certain conditions, when the rate of fire of the gun is constant and the rate of operation of the shutter system is a whole multiple of the rate of fire, a stroboscopic effect will be achieved which, as long as the gun is held stationary, will make the interrupted dashes as viewed through the sight appear to merge and to be standing in space. However, a certain irregularity of fire is usually the case during actual operation of the gun so that the visible dashes of each tracer cannot be expected to appear in the same relative position. Due, however, to the extended base of the objective viewing lenses, together with their magnifying power, depth perception is increased. The shutter enhances this increased depth perception by virtue of the fact that breaking up of the visible trajectory of the tracer bullets enables the eyes to establish definite points of focus which would be more difficult if the tracer trajectory were visible as a solid curved line.

While the invention has been described with reference to certain preferred examples thereof which give satisfactory results, it will be understood by those skilled in the art to which the invention pertains, after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is my intention, therefore, to cover in the appended claims all such changes and modifications.

The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes Without the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In a system of gunnery fire control the steps comprising firing a succession of projectiles from a gun at a moving target, rendering visible a portion of the trajectory of at least some of said projectiles, binocularly viewing said target and visible trajectory of said projectiles from said gun over converging lines of sight spaced along a base line normal to the bore of said gun at a distance exceeding the interpupillary distance whereby to increase the ability to perceive depth at the range of said target from said gun, periodically obscuring vision over said converging lines of sight for a predetermined interval to cause said visible portion of said trajectory to appear as a series of projectiles stationary in space, and thereafter directing said apparently stationary projectiles into intersection with said moving target.

2. In a system of gunnery fire control the steps comprising firing a succession of projectiles from a gun at a moving target, rendering visible a portion of the trajectory of at least some of said projectiles, binocularly viewing said target and visible trajectory from said gun along converging lines of sight that are spaced normal to the bore of said gun at a greater distance than the interpupillary distance so as to increase the depth perception at the range of said target from said gun, periodically obscuring said binocular vision co-incident with the firing of said succession of projectiles to cause said visible portion of said trajectory to be interrupted and to appear as a series of stationary projectiles, and thereafter directing said apparently stationary projectiles into intersection with said moving target.

THOMAS D. TYRA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,168,650 Kollmorgen Jan. 18, 1916 1,189,308 Sullivan July 4, 1916 1,609,233 Whidbourne et al. Nov. 30, 1926 1,746,179 Ashdown Feb. 4, 1930 1,814,756 Levy July 14, 1931 1,930,460 Boulin Oct. 17, 1933 2,157,575 Schmidt May 9, 1939 2,186,007 Chamberlin Jan. 9, 1940 2,276,270 Gregory Mar. 17, 1942 2,286,474 Durham et al June 16, 1942 FOREIGN PATENTS Number Country Date 514,532 France Nov. 16, 1920 780,117 France Jan. 24, 1935 441,773 Germany Mar. 15, 1927 431,991 Great Britain July 18, 1935 503,036 Great Britain Mar. 30, 1939 

